1. Field of the Invention
The present invention relates to a semiconductor manufacturing technique and, more particularly, to a semiconductor manufacturing apparatus which executes a plurality of processes such as an oxidation, a diffusion, and CVD (a Chemical Vapor Deposition) in a single chamber and a semiconductor device manufacturing method using the semiconductor manufacturing apparatus.
2. Description of the Related Art
In recent years, a technique for continuously executing a plurality of processes in a single chamber has been developed aiming at shortening the wafer process time in a semiconductor manufacturing apparatus. In such an apparatus, accurate control related to a film thickness and an impurity diffusion is required for the plurality of processes in the single chamber.
FIG. 7 is a flow chart showing the continuous process flow of the film formation process of an oxide film and SiN film based on a prior art. First, on the basis of technical experiences, the oxide film formation temperature, the oxidation gas flow rate, the oxidation time, the SiN deposition temperature, the SiN deposition time, the gas pressure in SiN film formation, the SiN film formation gas flow rate, and the like are input to the control computer of a semiconductor manufacturing apparatus (in this case, an oxidation/CVD furnace) by some means such that desired film thicknesses can be obtained, respectively. Next, a start signal is input by some means to start the process.
Processes such as a wafer loading into the apparatus, a heating up, a temperature retention, gas supplies, gas switchings, a cooling down, and a wafer unloading are performed in accordance with the set sequence. During the processes, the temperature in the furnace and the gas flow rate are kept at the set values as exactly as possible, and the oxidation time and deposition time are controlled, thereby obtaining the desired film thicknesses.
In the above sequence, however, a fluctuation in film thickness or a fluctuation in impurity dose due to uncontrollable disturbance factors in the apparatus or a fluctuation in film thickness or a fluctuation in impurity dose due to uncontrollable disturbance factors outside of the apparatus are not taken into consideration at all. Examples of uncontrollable disturbance factors in the apparatus are a slight change in temperature in heating due to the influence of the process temperature for the preceding batch and a very small change in gas flow rate due to a slight variation in supply voltage. An example of uncontrollable disturbance factors outside the apparatus is a change in the atmospheric pressure.
Since a feature size of devices is becoming finer, and these disturbance factors cannot be neglected nowadays, no sufficient element device performance and circuit characteristics can be obtained with the conventional film formation technique. For this reason, a semiconductor manufacturing apparatus control method that takes these disturbance factors into consideration has been demanded. In addition, since film thickness measurement, which is performed after the process, is not performed after the first film formation in the continuous process, more accurate film formation control is required.
To examine the influence of the above disturbance factors on the film thickness or impurity diffusion, calculation or simulation for an oxidation, a deposition, and an impurity diffusion is necessary. For example, Jpn. Pat. Appln. KOKAI Publication Nos. 11-288856 and 8-55145 describe ideas for comparing actual manufacturing data with simulated data. However, the purpose of comparison in these prior arts is to improve the accuracy of simulation or adjust simulated data to actual manufacturing data, which is anything but a proposal from the viewpoint of manufacturing control in changing manufacturing conditions or manufacturing parameters. In addition, no calculation is performed presuming disturbances inside and outside of the apparatus, so a variation in manufacturing each cycle is not taken into consideration.
As described above, in the conventional semiconductor manufacturing apparatus which continuously executes a plurality of processes related to manufacturing of a semiconductor device in a single chamber, a fluctuation in film thickness or a fluctuation in impurity dose due to uncontrollable disturbance factors in the apparatus or a fluctuation in film thickness or a fluctuation in impurity dose due to uncontrollable disturbance factors such as the atmospheric pressure outside of the apparatus occurs. For this reason, no sufficient element device performance and circuit characteristics can be obtained.